1. Field of the Invention
The present invention pertains to antimicrobial compositions of the type that may be used to control or destroy pathogenic microorganisms. More particularly, various antimicrobial agents are shown to work with cooperative effects against microorganisms in a wide variety of applications.
2. Description of the Related Art
Antimicrobial compositions are used to reduce the risk of infection. For example, antimicrobials are used to disinfect surfaces in hospitals, lavatories, food preparation facilities, and offices. Other uses include the control of pathogenic organisms on skin, where they may be used to reduce the transmission of disease or infection, e.g., as surgical scrub solutions or hand sanitizers. Antimicrobial compositions may also be used in veterinary applications for the control or prevention of hoof diseases, mastitis (in milk producing animals), or topical infections. Prevention of mastitis is a major goal of the dairy industry, where the disease may result from contact of the bovine or ovine mammary gland with pathogenic microorganisms, usually bacteria but occasionally yeast or fungi.
Mastitis is the single most costly disease affecting the dairy industry. Annual economic losses due to mastitis approximate $185 per dairy animal. This totals to approximately $1.7 billion annually for the entire United States market. Mastitis is always a potentially serious infection. Severe cases may cause death to the dairy animal. Milder cases are more common, but may have serious consequences, such as long term damage to the animal, loss of milk production for the dairy farmer and an unacceptable increase in veterinary costs.
To reduce mastitis, commercial teat dips have been developed which are usually administered to the teat by dipping, foaming, or spraying the teat prior to milking as well as after removal of the milking cup. Teat dips applied subsequent to milking may be in the form of lower viscosity dippable or sprayable compositions or in the form of a thick composition, film or barrier that remains on the teat until the next milking, which is generally 8 to 12 hours later.
Commercially available teat dips may be divided into two primary classifications, namely, non-barrier and barrier dips. The non-barrier teat dips are strictly antimicrobial and are applied to kill microorganisms that are already present in the teat canal or on the surface of the teat skin. By design, the microbiological effect is substantially immediate, targeting the contagious organisms that may be transferred between animals during the pre-milking, milking and post-milking process. The barrier dips may also be antimicrobial and are applied to form a prophylactic film or coating that may prevent microbes from contacting the teat. It is desirable to have an antimicrobial effect that remains active during the inter-milking period.
Teat dips have used a variety of antimicrobial agents. U.S. Pat. No. 2,739,922 issued to Shelanski describes the use of polymeric N-vinyl pyrrolidone in combination with iodophors. U.S. Pat. No. 3,993,777 issued to Caughman et al. describes the use of halogenated quaternary ammonium compounds. U.S. Pat. No. 4,199,602 issued to Lentsch describes the use of iodophors, chlorine releasing compounds (e.g. alkali hypochlorite), oxidizing compounds (e.g. hydrogen peroxide, peracids), protonated carboxylic acids (e.g. heptanoic, octanoic, nonanoic, decanoic, undecanoic acids), and nitroalkanols. U.S. Pat. No. 4,434,181 issued to Marks, Sr. et al. describes the use of acid anionics (e.g. alkylaryl sulfonic acids), chlorine dioxide (from alkali chlorite), and bisbiguanides such as chiorhexidine.
Some of the available teat dip agents suffer from serious drawbacks. For example, iodine, hypochlorite, chlorine dioxide, and hypochlorous acid are powerful disinfectants and strong oxidants, but they are also particularly noxious for both humans and animals. Chlorhexidine, for example, has become the focus of regulatory concern. Additionally, the use of overly powerful disinfectants may contribute to the mastitis problem by causing irritation of the teat skin, thus providing an opportunistic site which promotes infection. The Lentsch '602 patent recognizes that iodophors and such chlorine-based biocides as hypochlorite, chlorine dioxide, and hypochlorous acid have achieved the widest commercial acceptance; however, teat dips of the future may have to be iodine-free. Furthermore, the iodine-based and chlorine-based compositions may induce sensitized reactions in cow teats. This issue is of particular importance for barrier type products where the biocide may remain in contact with the skin during the 8-12 hour inter-milking period. On the other hand, less powerful teat dip agents, such as fatty acids and anionic surfactants, are often not broad enough in their antimicrobial spectrum to provide complete germicidal protection.
From a consumption point of view, it is known that relatively small quantities of iodine and chlorhexidine can result in taste changes of the milk as well as problems in the manufacture of dairy products. Furthermore, milk products must meet food and drug regulations which take into consideration ingestion of residual teat dip agents. There may be concern, for example, about increased iodine consumption because iodine is linked to thyroid function and it is recommended that some populations, such as pregnant women, limit their intake. Also, iodine associates with problems of staining, and some operators/users develop allergic symptoms such as skin irritation and sensitization from iodine-based product use.
There is a need for compositions that are effective broad spectrum antimicrobials that provide extended germicidal activity and are non-irritating to skin.